| Nicotiana tobacum,as one of economic crops is widely cultivated in the world,which have the characteristics of short growth cycle and preferable environmental adaptability.The release of the tobacco genome provides significant information for identifying stress resistance genes and selecting excellent varieties.The bZIP?basic leucine zipper?proteins as a transcription factors ubiquitous distributes in animals and plants,which play crucial roles in carbohydrate synthesis,vascular bundle growth,flower organ development,metabolism of various biological hormones,and responses to abiotic stress.In this study,the genome of tobacco K326 was reannotated based on the released genome sequences.The bZIP transcription factor family members were identified in tobacco by comparative genomics,and investigated their evolutionary history and protein function by phylogenetic analysis,conservative domain analysis,genetic structure analysis and protein interaction network analysis.In addition,according to the fluorescence quantitative experiments and transcriptome data,the expression pattern of bZIP genes in tobacco was studied.The results were as follows:?1?To re-annotate the K326 genome for protein-coding genes,the strategy of ab initio predictors were used.A total of 64,587 genes were predicted.The results showed that tobacco genome contained lots of repetitive sequences,and the coverage of these repetitive sequences reached more than 70 percent.At the same time,the completeness of K326protein sequences were evaluated.The novel annotated version contained 2,959 protein coding sequences,which completeness achieved 97%.?2?According to the bZIP gene in Arabidopsis as the reference sequences,140NtbZIP genes were identified in tobacco.All bZIP genes contained bZIP protein functional domain,and these gene lengths ranged from 118 to 1,235 amino acids.Gene exons number ranged from 1 to 17.Phylogenetic results revealed that all the NtbZIPs can generally be separated into 10 subfamilies.A and D subfamilies had more gene members,and B,C,F and H subfamilies had fewer members.These results showed the kinship of different members at the systematic evolution level.?3?The motifs and exon/intron distribution of NtbZIP genes from the same subfamilies owned the similar structure.The conservative domain analysis revealed that a total of 20 typical motifs were identified.Motif 1 was discovered in almost all of NtbZIP members,which is widely distributed in NtbZIPs.The increase or loss of exons/introns can lead to the complexity of gene function.The gene structure analysis showed that these introns distributed in different subfamilies were obviously different.However,the bZIP genes in the same subfamily were highly conserved.In addition,bZIP genes in group F showed the most stable numbers of exon with only one exon,that might because of a partial loss in the course of evolution.?4?Comparing to Arabidopsis thaliana orthologous genes,the bZIP protein interaction network was predicted.The results showed that 42 network nodes were predicted,and a lot of protein interactions were existed between these nodes.These proteins ware closely related to the formation of abscisic acid metabolic pathways,the formation of cryptochrome,the growth and development of seeds,and the maturation of flower organs.?5?The expression profile of bZIP transcription factor was analyzed,and 28 genes were showed in all tested tissues.These bZIP protein genes might play crucial roles in the formation of nutrients,and involved in tobacco oxidation resistance,pathogen defense and the number of leaves'growth.In addition,bZIP transcription factors can respond to multiple stimuli of abiotic stresses.Twenty-one genes showed various expression levels at least in a condition,which were treated by NaCl,PEG and NaHCO3 solution.11 genes can be significantly expressed by two or three treatments.These results indicated that bZIP transcription factors in tobacco can respond to various environmental stresses and participate in the regulation of various abiotic stresses. |
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